#!/usr/bin/python3
# filename:username.py

import subprocess
username = input("please input username:")
f_passwd = subprocess.getoutput("cat /etc/passwd")
f_lines = f_passwd.splitlines()
a = [i.split(":")[0] for i in f_lines]
if username in a:
    print ("the user %s is exist" % username)
else:
    print ("the user %s not exist" % username)
